Electronic device

ABSTRACT

An electronic device includes: a substrate having an upper surface and a lower surface; a first electronic component mounted on the upper surface of the substrate; a second electronic component mounted on the lower surface of the substrate; and a mold portion covering the second electronic component without covering the first electronic component. The first electronic component is bonded to the upper surface on the first relative surface via a conductive first bonding member. The second electronic component is bonded to the lower surface via a second bonding member on a second relative surface relative to the lower surface.

The present application is based on, and claims priority from JP Application Serial Number 2020-152562, filed Sep. 11, 2020, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND 1. Technical Field

The present disclosure relates to an electronic device.

2. Related Art

A piezoelectric device disclosed in JP-A-2007-173431 includes a substrate, a piezoelectric vibrator and a semiconductor chip mounted on an upper surface of the substrate, and a mold material for molding the piezoelectric vibrator and the semiconductor chip. The piezoelectric vibrator is bonded to the substrate via solder, and the solder serves as a spacer to form a minute gap between the substrate and the piezoelectric vibrator.

However, in the above-described configuration, since the gap between the substrate and the piezoelectric vibrator is minute, filling of the mold material into the gap is insufficient, and the gap may not be completely filled. As described above, when the piezoelectric device in which the gap between the substrate and the piezoelectric vibrator is not completely filled with the mold material is solder-mounted on an external substrate such as a motherboard, the solder bonding the piezoelectric vibrator and the substrate may be melted by the heat, and the melted solder may wet and spread in the gap to cause a short circuit.

SUMMARY

An electronic device according to the present disclosure includes: a substrate having a first surface and a second surface that are in a front and back relationship with each other, a first wiring pattern being disposed on the first surface, and a second wiring pattern being disposed on the second surface; a first electronic component mounted on the first surface of the substrate; a second electronic component mounted on the second surface of the substrate; and a mold portion that covers the second electronic component without covering the first electronic component, in which the first electronic component includes a first mounting terminal disposed on a first relative surface relative to the first surface, and is bonded to the first surface on the first relative surface via a conductive first bonding member, and the first mounting terminal and the first wiring pattern are electrically coupled to each other via the first bonding member, and the second electronic component includes a second mounting terminal, and is bonded to the second surface via a second bonding member on a second relative surface relative to the second surface, and the second mounting terminal and the second wiring pattern are electrically coupled to each other via a conductive wire.

An electronic device according to the present disclosure includes: a substrate having a first surface and a second surface that are in a front and back relationship with each other, a first wiring pattern being disposed on the first surface, and a second wiring pattern being disposed on the second surface; a first electronic component mounted on the first surface of the substrate; a second electronic component mounted on the second surface of the substrate; and a mold portion that covers the second electronic component without covering the first electronic component, in which the first electronic component includes a first mounting terminal disposed on a first relative surface relative to the first surface, and is bonded to the first surface on the first relative surface via a conductive first bonding member, and the first mounting terminal and the first wiring pattern are electrically coupled to each other via the first bonding member, and the second electronic component includes a second mounting terminal disposed on a second relative surface relative to the second surface, and is bonded to the second surface on the second relative surface via a conductive second bonding member having a melting point higher than that of the first bonding member, and the second mounting terminal and the second wiring pattern are electrically coupled to each other via the second bonding member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing an electronic device according to a first embodiment.

FIG. 2 is a plan view showing inside of a cap of the electronic device shown in FIG. 1.

FIG. 3 is a cross-sectional view taken along a line A-A in FIG. 2.

FIG. 4 is a flowchart showing manufacturing steps of the electronic device shown in FIG. 1.

FIG. 5 is a plan view showing a lead frame.

FIG. 6 is a cross-sectional view for illustrating a method of manufacturing the electronic device.

FIG. 7 is a cross-sectional view for illustrating the method of manufacturing the electronic device.

FIG. 8 is a cross-sectional view for illustrating the method of manufacturing the electronic device.

FIG. 9 is a cross-sectional view for illustrating the method of manufacturing the electronic device.

FIG. 10 is a cross-sectional view for illustrating the method of manufacturing the electronic device.

FIG. 11 is a cross-sectional view showing an electronic device according to a second embodiment.

FIG. 12 is a cross-sectional view showing an electronic device according to a third embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an electronic device according to an aspect of the present disclosure will be described in detail based on an embodiment illustrated in the accompanying drawings. For convenience of illustration, three axes orthogonal to one another are illustrated as an X axis, a Y axis, and a Z axis in each of the drawings except for FIG. 4. A direction parallel to the X axis is also referred to as an “X axis direction”. A direction parallel to the Y axis is also referred to as a “Y axis direction”. A direction parallel to the Z axis is also referred to as a “Z axis direction”. A tip end side of an arrow indicating each axis is also referred to as a “positive side”. An opposite side thereof is also referred to as a “negative side”. The positive side in the Z axis direction is also referred to as “upper”. The negative side in the Z axis direction is also referred to as “lower”.

First Embodiment

FIG. 1 is a perspective view showing an electronic device according to a first embodiment. FIG. 2 is a plan view showing inside of a cap of the electronic device shown in FIG. 1. FIG. 3 is a cross-sectional view taken along a line A-A in FIG. 2. FIG. 4 is a flowchart showing manufacturing steps of the electronic device shown in FIG. 1. FIG. 5 is a plan view showing a lead frame. FIGS. 6 to 10 are cross-sectional views for illustrating a method of manufacturing the electronic device. In FIG. 2, a first wiring pattern is not shown for convenience of illustration.

An electronic device 1 shown in FIG. 1 has a quad flat package (QFP) structure. As shown in FIGS. 2 and 3, the electronic device 1 includes a substrate 2, a first electronic component 3 located on an upper surface 21 side of the substrate 2 and bonded to the upper surface 21, a second electronic component 4 located on a lower surface 22 side of the substrate 2 and bonded to the lower surface 22, a lead group 7 including a plurality of leads 71 bonded to the lower surface 22 of the substrate 2, a cap 8 covering the substrate 2 so as to cover the first electronic component 3, and a mold portion 9 that molds and seals the second electronic component 4 and bonds the cap 8 to the substrate 2. The electronic device 1 includes three angular velocity sensors 3 x, 3 y, and 3 z as the first electronic component 3, and includes an acceleration sensor 5 and a circuit element 6 as the second electronic component 4.

The substrate 2 has a substantially square plate shape in a plan view, and has the upper surface 21 as a first surface and the lower surface 22 as a second surface which are in a front and back relationship with each other. The substrate is a ceramic substrate and is made of various ceramic materials such as alumina and titania. When the ceramic substrate is used as the substrate 2, the substrate 2 has high corrosion resistance. The substrate 2 having excellent mechanical strength is obtained. Since moisture absorption is less likely to occur and heat resistance is excellent, damage due to heat applied at the time of manufacturing the electronic device 1 is less likely to occur. By using the same material as that of a base 32 included in the angular velocity sensors 3 x, 3 y, and 3 z, thermal stress due to a linear expansion coefficient difference is less likely to occur therebetween. Therefore, the electronic device 1 having excellent long-term reliability is obtained. The substrate 2 is not limited to a ceramic substrate. For example, various semiconductor substrates, various glass substrates, and various printed substrates can also be used.

A first wiring pattern 28 electrically coupled to the first electronic component 3 is disposed on the upper surface 21 of the substrate 2. On the other hand, a second wiring pattern 29 electrically coupled to the second electronic component 4 is disposed on the lower surface 22 of the substrate 2. The first wiring pattern 28 is electrically coupled to the second wiring pattern 29 via a through electrode, which is not shown, formed in the substrate 2.

The first electronic component 3 is a packaged surface mount component. Accordingly, it is possible to exhibit higher mechanical strength than a mount component in which an element is exposed. The first electronic component can be easily mounted on the substrate 2. The first electronic component 3 is a physical quantity sensor. In particular, in the present embodiment, three angular velocity sensors 3 x, 3 y, and 3 z are provided. The angular velocity sensor 3 x is a sensor that detects an angular velocity around the X axis. The angular velocity sensor 3 y is a sensor that detects an angular velocity around the Y axis. The angular velocity sensor 3 z is a sensor that detects an angular velocity around the Z axis. By using the first electronic component 3 as the physical quantity sensor, the electronic device 1 that is suitably mounted on various electronic devices and mobile bodies is obtained. Therefore, convenience and demand of the electronic device 1 are increased. In particular, since the electronic device 1 can detect the angular velocities about three axes orthogonal to one another, the above effect is more remarkable.

Basic configurations of the angular velocity sensors 3 x, 3 y, and 3 z are the same as one another. The angular velocity sensors 3 x, 3 y, and 3 z are mounted in different postures so that detection axes face the X-axis direction, the Y-axis direction, and the Z-axis direction. As shown in FIG. 3, each of the angular velocity sensors 3 x, 3 y, and 3 z includes a package 31 and a physical quantity detection element 34 accommodated in the package 31. The package 31 includes a box-shaped base 32 having a recess 321, and a lid 33 bonded to the base 32 so as to close an opening of the recess 321. The base 32 is constituted by a ceramic material such as alumina. The lid 33 is constituted by a metal material such as Kovar.

As shown in FIG. 3, a plurality of first mounting terminals 39 electrically coupled to the physical quantity detection element 34 are disposed on a lower surface of the package 31, that is, a first relative surface 320 relative to the upper surface 21 of the substrate 2. The physical quantity detection element 34 is, for example, a crystal vibration element having a drive arm and a vibration arm. In such a crystal vibration element, when the angular velocity around the detection axis is applied in a state where a drive signal is applied to drive and vibrate the drive arm, detection vibration is excited in the detection arm by Coriolis force. Electric charge generated in the detection arm by the detection vibration is extracted as a detection signal. The angular velocity can be obtained based on the extracted detection signal.

Each of the angular velocity sensors 3 x, 3 y, and 3 z is bonded to the upper surface 21 of the substrate 2 via a conductive first bonding member B1 on the first relative surface 320. The first mounting terminal 39 of each of the angular velocity sensors 3 x, 3 y, and 3 z is electrically coupled to the first wiring pattern 28 via the first bonding member B1. The first bonding member B1 is solder, and mechanically and electrically couples the angular velocity sensors 3 x, 3 y, and 3 z to the substrate 2 by solder reflow. Accordingly, it is possible to easily and accurately couple the angular velocity sensors 3 x, 3 y, and 3 z to the substrate 2. The first bonding member B1 is less deteriorated over time and has high reliability. The first bonding member B1 is not limited to solder. For example, various brazing materials such as gold brazing filler and silver brazing filler, various metal bumps such as gold bumps and silver bumps, and various conductive adhesives in which a conductive filler is dispersed in a resin-based adhesive can be used.

Although the angular velocity sensors 3 x, 3 y, and 3 z are described above, the configurations of the angular velocity sensors 3 x, 3 y, and 3 z are not particularly limited. For example, the physical quantity detection element 34 may be formed of a capacitive silicon vibration element and detect the angular velocity based on a change in capacitance. At least one of the angular velocity sensors 3 x, 3 y, and 3 z may be different from the other angular velocity sensors. In the first electronic component 3, at least one of the angular velocity sensors 3 x, 3 y, and 3 z may be omitted. The first electronic component 3 may be a physical quantity sensor that detects a physical quantity other than the angular velocity, or may not be a physical quantity sensor. The first electronic component 3 does not have to be a packaged surface mount component. For example, the package 31 may be omitted and the physical quantity detecting element 34 may be exposed in the cap 8.

As shown in FIG. 3, the cap 8 is bonded to the substrate 2, and accommodates the angular velocity sensors 3 x, 3 y, and 3 z between the cap 8 and the substrate 2. The cap 8 has a hat shape, and includes a base portion 81 having a recess 811 that opens to the upper surface 21 side, and an annular flange portion 82 protruding from a lower end portion of the base portion 81 toward an outer peripheral side. The cap 8 is disposed on the upper surface 21 of the substrate 2 so as to accommodate the angular velocity sensors 3 x, 3 y, and 3 z in the recess 811. The flange portion 82 is in contact with the upper surface 21. Then, the cap 8 and the substrate 2 are bonded to each other by the mold portion 9, and the inside of the recess 811 is hermetically sealed.

In this way, by providing the cap 8 that accommodates the angular velocity sensors 3 x, 3 y, and 3 z, the angular velocity sensors 3 x, 3 y, and 3 z can be protected from moisture, dust, impact, and the like. In the present embodiment, the inside of the recess 811 is air-sealed. The present disclosure is not limited thereto. For example, sealing under reduced pressure or sealing under positive pressure may be performed, or the gas may be replaced with a stable gas such as nitrogen or argon.

The cap 8 has conductivity and is formed of, for example, a metal material. In particular, in the present embodiment, the cap 8 is formed of a 42 alloy which is an iron-nickel alloy. Accordingly, the linear expansion coefficient difference between the substrate 2 formed of the ceramic substrate and the cap 8 can be made sufficiently small. Generation of thermal stress due to the linear expansion coefficient difference can be effectively prevented. Therefore, the electronic device 1 is hardly affected by an environmental temperature and has stable characteristics. The cap 8 is coupled to aground (GND) when the electronic device 1 is used. Accordingly, the cap 8 functions as a shield that blocks electromagnetic noise from the outside. Driving of the angular velocity sensors 3 x, 3 y, and 3 z accommodated in the cap 8 is stabilized. A constituent material of the cap 8 is not limited to the 42 alloy. For example, a metal material such as a SUS material, various ceramic materials, various resin materials, a semiconductor material such as silicon, and various glass materials can also be used.

Here, as a method of bonding the cap 8 and the substrate 2, there is a method of using an adhesive disposed between the flange portion 82 and the substrate 2, particularly an adhesive containing an organic component such as a resin-based adhesive. However, in the present embodiment, such a method is not adopted, and the cap 8 and the substrate 2 are bonded by the mold portion 9. Accordingly, it is possible to reduce a height of the electronic device 1 as compared with the method in which the adhesive is disposed between the flange portion 82 and the substrate 2. There is no risk that the inside of the cap 8 may be contaminated by outgas containing the organic component generated from the adhesive. It is also possible to prevent a decrease in the reliability due to aged deterioration of the adhesive. Therefore, the electronic device 1 is small and has high reliability. Further, since no adhesive is used, the manufacturing cost of the electronic device 1 can be reduced. The method of bonding the cap 8 and the substrate 2 is not particularly limited.

In the electronic device 1, the recess 811 is a gap and is not filled with the mold portion 9. That is, the angular velocity sensors 3 x, 3 y, and 3 z accommodated in the cap 8 are not covered with the mold portion 9. Therefore, the problem described in the related art, that is, the problem that the mold material cannot be fully filled in the gap formed between the angular velocity sensors 3 x, 3 y, and 3 z and the substrate 2 due to the thickness of the first joining member B1, and a minute gap is formed in the portion does not occur. Therefore, even if the first bonding member B1 is melted by heat applied when the electronic device 1 solder-mounted on an external substrate, unlike the related art, wetting and spreading of the melted first bonding member B1 to an unintended portion is prevented. Therefore, it is possible to prevent the occurrence of electrical defects such as a short circuit, a disconnection, and an increase in wiring resistance.

As shown in FIGS. 2 and 3, the second electronic component 4 includes the acceleration sensor 5 and the circuit element 6. Since the electronic device 1 includes the circuit element 6, the angular velocity sensors 3 x, 3 y, and 3 z and the acceleration sensor 5 can be coupled to the circuit element 6 in the electronic device 1. Therefore, a wiring length for coupling the components can be shortened. Therefore, in particular, noise is less likely to be added to detection signals output from the angular velocity sensors 3 x, 3 y, and 3 z and the acceleration sensor 5, and the angular velocity around each axis and the acceleration in each axis direction can be more accurately detected.

As shown in FIG. 3, the acceleration sensor 5 is bonded to the lower surface 22 via a second bonding member B2 on an upper surface thereof, that is, a second relative surface 50 relative to the lower surface 22 of the substrate 2. The circuit element 6 is bonded to the lower surface of the acceleration sensor 5 via a third bonding member B3 on an upper surface thereof, that is, a third relative surface 60 relative to the lower surface of the acceleration sensor 5. In the present embodiment, since a shape of the acceleration sensor 5 in the plan view is larger than a shape of the circuit element 6 in the plan view, the acceleration sensor 5 is bonded to the substrate 2, and the circuit element 6 is bonded to the acceleration sensor 5. Accordingly, the acceleration sensor 5 and the circuit element 6 can be disposed on the substrate 2 in a well-balanced manner.

Here, the second bonding member B2 and the third bonding member B3 are not electrically coupled. Therefore, as the second bonding member B2 and the third bonding member B3, for example, various die attach agents, and various die attach films can be used regardless of whether the second bonding member B2 and the third bonding member B3 are conductive or not.

The acceleration sensor 5 is a three-axis acceleration sensor capable of independently detecting an acceleration in the X axis direction, an acceleration in the Y axis direction, and an acceleration in the Z axis direction. That is, the electronic device 1 is a six-axis composite sensor capable of detecting the angular velocity around each axis of the X axis, the Y axis, and the Z axis and the acceleration in each axis direction. In this way, by making the electronic device 1 usable as the physical quantity sensor, the electronic device 1 can be mounted on various electronic components and has high convenience and demand.

The acceleration sensor 5 includes a package 51 and sensor elements 54, 55, and 56 accommodated in the package 51. The package 51 includes a base 52 having a recess 521 formed so as to overlap the sensor elements 54, 55, and 56, and a lid 53 having a recess 531 that opens to a base 52 side and bonded to the base 52 so as to accommodate the sensor elements 54, 55, and 56 in the recess 531. A part of a lower surface of the base 52 is exposed from the lid 53. A plurality of mounting terminals 59 electrically coupled to the sensor elements 54, 55, and 56 are disposed in the exposed part.

The sensor element 54 is an element that detects the acceleration in the X axis direction. The sensor element 55 is an element that detects the acceleration in the Y axis direction. The sensor element 56 is an element that detects the acceleration in the Z axis direction. Each of the sensor elements 54, 55, and 56 is a silicon vibration element including a fixed electrode fixed to the base 52 and a movable electrode variable with respect to the base 52. When the acceleration in the detection axis direction is received, the movable electrode is displaced with respect to the fixed electrode, and the capacitance formed between the fixed electrode and the movable electrode changes. Therefore, a change in the capacitance of each of the sensor elements 54, 55, and 56 is extracted as the detection signal. The acceleration in each axis direction can be obtained based on the extracted detection signal.

Although the acceleration sensor 5 is described above, the configuration of the acceleration sensor 5 is not particularly limited as long as the acceleration sensor 5 can exhibit its function. For example, the sensor elements 54, 55, and 56 are not limited to the silicon vibration elements, and may be, for example, crystal vibration elements, and may be constituted to detect the acceleration based on the electric charge generated by vibration.

The circuit element 6 is an unpackaged semiconductor chip, that is, a bare chip. Accordingly, it is possible to reduce size and cost of the circuit element 6. The circuit element 6 is not limited to the bare chip, and may be a packaged element. The circuit element 6 includes a control circuit 61 that controls driving of the angular velocity sensors 3 x, 3 y, and 3 z and the acceleration sensor 5, and an interface circuit 62 that performs communication with the outside. The control circuit 61 independently controls the driving of the angular velocity sensors 3 x, 3 y, and 3 z and the acceleration sensor 5, and independently detects the angular velocity around each axis of the X axis, the Y axis, and the Z axis and the acceleration in each axis direction based on the detection signals output from the angular velocity sensors 3 x, 3 y, and 3 z and the acceleration sensor 5. The interface circuit 62 transmits and receives signals, receives a command from an external device, and outputs the detected angular velocity and acceleration to the external device. A communication method of the interface circuit 62 is not particularly limited. In the present embodiment, serial peripheral interface (SPI) communication is used. The SPI communication is a communication method suitable for coupling a plurality of sensors. Since all signals related to the angular velocity and the acceleration can be output from one lead 71, pin saving of the electronic device 1 can be achieved.

The circuit element 6 includes a plurality of second mounting terminals 69 disposed on a lower surface thereof. The circuit element 6 is electrically coupled to the acceleration sensor 5 and the second wiring pattern 29 via a bonding wire BW. Accordingly, the circuit element 6 is electrically coupled to the angular velocity sensors 3 x, 3 y, and 3 z, the acceleration sensor 5, and the lead 71.

The lead group 7 is located on the lower surface 22 side of the substrate 2, and includes a plurality of leads 71 bonded to the substrate 2 via a conductive fourth bonding member B4. The plurality of leads 71 are provided substantially uniformly along the four sides of the substrate 2. At least a part of the plurality of leads 71 is electrically coupled to the second wiring pattern 29 via the fourth bonding member B4, and is electrically coupled to the circuit element 6 via the second wiring pattern 29 and the bonding wire BW. The fourth bonding member B4 is solder, and performs mechanical coupling and electrical coupling between the lead 71 and the substrate 2 by solder reflow. Accordingly, it is possible to easily and accurately couple the lead 71 and the substrate 2. The fourth bonding member B4 is less deteriorated over time and has high reliability. The fourth bonding member B4 is not limited to solder. For example, various brazing materials such as gold brazing filler and silver brazing filler, various metal bumps such as gold bumps and silver bumps, and various conductive adhesives in which a conductive filler is dispersed in a resin-based adhesive can be used.

A free end portion of each lead 71 protrudes to the outside of the mold portion 9, and the lead 71 is attached to the external device at this portion. That is, the electronic device 1 is a quad flat package (QFP). In the present embodiment, each lead 71 protruding from the mold portion 9 is bent downward in the middle thereof. However, the shape of each lead 71 is not particularly limited, and may be, for example, straight or bent upward. The electronic device 1 is not limited to the QFP, and may be, for example, a plastic leaded chip carrier (PLCC) in which the lead 71 protruding from the mold portion 9 is folded back to the lower side of the substrate 2.

The mold portion 9 molds the acceleration sensor 5 and the circuit element 6, and protects the acceleration sensor 5 and the circuit element 6 from moisture, dust, impact, and the like. The mold portion 9 molds a coupling portion between the substrate 2 and each lead 71, and protects the coupling portion from moisture, dust, impact, and the like. The mold portion 9 bonds the cap 8 and the substrate 2. A mold material constituting the mold portion 9 is not particularly limited. For example, a thermosetting epoxy resin or a curable resin material can be used. The mold portion 9 can be formed by, for example, a transfer molding method.

Here, as described above, the second electronic component 4 covered with the mold portion 9 is electrically coupled by the bonding wire BW. Therefore, even if the minute gap is formed in the mold portion 9 without being filled with the mold material and the second and third bonding members B2 and B3 melted by heat at the time of solder-mounting wet and spread in the minute gap, the electrical defects such as the short circuit, the disconnection, and the increase in the wiring resistance do not substantially occur.

The mold portion 9 includes a base portion 91 that is located on the lower surface 22 side of the substrate 2 and molds the second electronic component 4, and a fixing portion 92 that is located on the side of the substrate 2, molds a coupling portion between the substrate 2 and the lead 71, and bonds the substrate 2 and the cap 8. The fixing portion 92 has a substantially C-shaped cross section, bypasses the side of the substrate 2 from the lower surface 22 of the substrate 2 and goes around to the upper surface 21 side, and molds the flange portion 82 of the cap 8 to bond the substrate 2 and the cap 8.

According to such a configuration, as described above, it is not necessary to dispose the adhesive between the substrate 2 and the cap 8 when the substrate 2 and the cap 8 are bonded to each other. Therefore, the height of the electronic device 1 can be reduced. There is no risk that the inside of the cap 8 may be contaminated by the outgas generated from the adhesive. Therefore, the electronic device 1 is small and has high reliability. In particular, by molding the flange portion 82, the gap between the cap 8 and the substrate 2 can be closed by the mold material, so that the inside of the cap 8 can be hermetically sealed more reliably.

The mold portion 9 molds only from a central portion to an outer peripheral side end portion of the flange portion 82, and a portion on the inner peripheral side of the flange portion 82 is not molded. That is, the flange portion 82 includes a mold region 821 covered with the mold portion 9 and a non-mold region 822 not covered with the mold portion 9. The mold region 821 is provided on the outer peripheral side of the flange portion 82 with respect to the non-mold region 822. By forming the non-mold region 822 in the flange portion 82 in this way, as will be described later, when the mold portion 9 is formed, the cap can be easily supported by the mold, the manufacturing of the electronic device 1 is facilitated, and accuracy thereof is improved.

Next, a method of manufacturing the electronic device 1 will be described. As shown in FIG. 4, the manufacturing step of the electronic device 1 includes a preparation step S1 of preparing the substrate 2 on which the first electronic component 3 and the second electronic component 4 are mounted and to which the leads 71 are bonded, a molding step S2 of forming the mold portion 9 in a state where the substrate 2 is covered with the cap 8, and a lead shaping step S3 of shaping the leads 71.

Preparation Step S1

First, the substrate 2 is prepared in which the first wiring pattern 28 is formed on the upper surface 21, the second wiring pattern 29 is formed on the lower surface 22, and the first wiring pattern 28 and the second wiring pattern 29 are electrically coupled to each other by a through electrode which is not shown. Next, a lead frame 70 shown in FIG. 5 is prepared. The lead frame 70 includes a frame-shaped frame 73, the plurality of leads 71 located inside the frame 73 and supported by the frame 73, and tie bars 74 coupling the plurality of leads 71.

Next, as shown in FIG. 6, the leads 71 are bonded to the lower surface 22 of the substrate 2 via the fourth bonding member B4. Specifically, a cleaning solder paste is used as the fourth bonding member B4. The leads 71 are bonded to the substrate 2 by the solder reflow. A narrow constriction portion is formed on an immediate tip end side of the bonding portion of each lead 71 to the substrate 2. Accordingly, it is possible to prevent wetting and spreading of the fourth bonding member B4 to the tip end side of the lead 71 at the time of the solder reflow.

Next, a flux residue generated by the solder reflow is cleaned and removed. Accordingly, the mold material is easily filled in the portion, so that the mold portion 9 with higher accuracy can be formed. It is also possible to effectively prevent corrosion or the like caused by re-melting of the flux residue at the time of subsequent solder reflow.

Next, the angular velocity sensors 3 x, 3 y, and 3 z are prepared, and are mounted on the upper surface 21 of the substrate 2 via the first bonding member B1 as shown in FIG. 7. Specifically, a non-cleaning solder paste is used as the first bonding member B1. The angular velocity sensors 3 x, 3 y, and 3 z are bonded to the substrate 2 by the solder reflow. Unlike the case of the lead 71, the flux residue generated by the solder reflow is not cleaned and removed, and a solder mounting surface is kept covered with the flux residue. Accordingly, contact between the portion and the atmosphere can be prevented, and corrosion of the portion can be effectively prevented.

As described above, after the leads 71 are bonded to the substrate 2 by the solder reflow, the angular velocity sensors 3 x, 3 y, and 3 z are bonded to the substrate 2 by the solder reflow, so that thermal damage to the angular velocity sensors 3 x, 3 y, and 3 z can be reduced. Therefore, it is possible to effectively prevent deterioration or fluctuation of the characteristics of each of the angular velocity sensors 3 x, 3 y, and 3 z.

Next, the acceleration sensor 5 and the circuit element 6 are prepared. As shown in FIG. 8, the acceleration sensor 5 is bonded to the lower surface 22 of the substrate 2 via the second bonding member B2. The circuit element 6 is bonded to the lower surface of the acceleration sensor 5 via the third bonding member B3. As the second and third bonding members B2 and B3, the die attach agent, the die attach film, or the like can be used.

After curing of the second and third bonding members B2 and B3 is completed, the bonding wire BW is formed to electrically couple each portion. A wire bonding step can be performed, for example, in a state where the substrate 2 is mounted on a heater block 1100 having a recess for preventing interference with the angular velocity sensors 3 x, 3 y, and 3 z, and the substrate 2 is fixed by a clamper 1200. A heating temperature of the substrate 2 is set to a relatively low temperature, for example, about 180° C. or more and 200° C. or less. Accordingly, thermal damage to the angular velocity sensors 3 x, 3 y, and 3 z, the acceleration sensor 5, and the circuit element 6 can be reduced.

Molding Step S2

Next, the substrate 2 is molded in a state where the substrate 2 is covered with the cap 8 to form the mold portion 9. In this step, a mold 2000 shown in FIG. 9 is used. The mold 2000 includes a lower mold 2100 and an upper mold 2200.

The lower mold 2100 includes a cap mounting portion 2110 on which the cap 8 is mounted, a mold material filling portion 2130 that is located outside the cap mounting portion 2110 and forms a space to be filled with the mold material, and a lead support portion 2140 that is located outside the mold material filling portion 2130 and supports the lead 71.

The cap mounting portion 2110 includes a recess 2111 that opens on an upper surface side of the lower mold 2100 and has a shape conforming to an outer shape of the base portion 81 of the cap 8, and a support portion 2112 that is located outside the recess 2111 and supports the flange portion 82 of the cap 8 from below. In a state in which the cap 8 is mounted in the cap mounting portion 2110, the support portion 2112 comes into contact with the non-mold region 822 of the flange portion 82, that is, a portion from the central portion to the inner peripheral side end portion of the flange portion 82, and supports the portion from below. In this way, by supporting the flange portion 82 located at an outer edge portion of the cap 8, a posture of the cap 8 is stabilized. Further, since the flange portion 82 is also a portion that comes into contact with the substrate 2, a posture of the substrate 2 mounted on the cap 8 is stabilized by supporting the flange portion 82. Therefore, the substrate 2 can be accurately located with respect to the cap 8. What is important here is that the support portion 2112 does not come into contact with the mold region 821 of the flange portion 82, that is, the portion from the central portion to the outer peripheral side end portion of the flange portion 82.

The mold material filling portion 2130 is constituted by a recess recessed from the support portion 2112, and overlaps the mold region 821 of the flange portion 82, that is, the portion from the central portion to the outer peripheral side end portion of the flange portion 82 in the plan view. The mold material filling part 2130 forms a gap for pouring the mold material between the mold region 821 of the flange portion 82 and the lower mold 2100. The lead support portion 2140 is located below the lead 71 and supports the lead 71 by sandwiching the lead 71 between the lead support portion 2140 and the upper mold 2200. In a state in which the substrate 2 is merely mounted on the lower mold 2100, that is, in a state in which the upper mold 2200 is not set, the lead support portion 2140 is not in contact with the lead 71, and a gap G is formed therebetween.

On the other hand, the upper mold 2200 includes a mold material filling portion 2210 that forms a space for filling the mold material around the second electronic component 4, and a lead pressing portion 2220 that is located outside the mold material filling portion 2210 and presses the lead 71 toward the lead support portion 2140. The mold material filling portion 2210 is constituted by a recess that opens to a lower surface side. In a state in which the upper mold 2200 is set in the lower mold 2100, the second electronic component 4 and a base end portion of each lead 71 are accommodated in the recess. Further, the mold material filling portion 2210 is coupled to the mold material filling portion 2130 at an outer edge portion thereof. One space to be filled with the mold material is formed by the mold material filling portions 2210 and 2130.

In this step, first, the cap 8 is mounted in the cap mounting portion 2110, and then the substrate 2 is mounted on the cap 8. The cap 8 may be mounted in the cap mounting portion 2110 after the substrate 2 is mounted on the cap 8.

Next, as shown in FIG. 10, the upper mold 2200 is set on the lower mold 2100. In a state where the upper mold 2200 is set on the lower mold 2100, the lead 71 is pressed toward the lead support portion 2140 by the lead pressing portion 2220 and is pressed against the lead support portion 2140. Since the gap G is formed between the lead 71 and the lead support portion 2140, the lead 71 is elastically deformed downward and is sandwiched between the lead support portion 2140 and the lead pressing portion 2220 in this state. Therefore, a restoring force F for returning to a natural state is generated in the lead 71, and the substrate 2 is biased toward the cap 8 by the restoring force F and is pressed against the cap 8. Accordingly, the cap 8 and the substrate 2 are brought into close contact with each other. Therefore, intrusion of the mold material into the cap 8 can be effectively prevented, and the cap 8 can be hermetically sealed more reliably.

In this state, the mold material filling portions 2210 and 2130 are filled with the heated and softened mold material, and the mold portion 9 is formed by cooling and curing the mold material. Accordingly, the mold portion 9 that covers the second electronic component 4 and bonds the cap 8 and the substrate 2 is formed. In particular, since the mold region 821 is located on the outer peripheral side of the flange portion 82 with respect to the non-mold region 822, the bonding of the cap 8 and the substrate 2 and the hermetical sealing of the cap 8 can be easily and more reliably performed.

Lead Shaping Step S3

Next, the frame 73 is removed from the lead frame 70, and the lead 71 is bent into a predetermined shape. Next, the tie bar 74 coupling the leads 71 to each other is cut by a laser, a trim mold, or the like. Accordingly, the electronic device 1 shown in FIG. 1 is manufactured.

According to such a manufacturing method, it is possible to more easily manufacture the electronic device 1 in which the electrical defects such as the short circuit, the disconnection, and the increase in the wiring resistance are less likely to occur.

The configuration and the manufacturing method of the electronic device 1 are described above. As described above, the electronic device 1 includes: the substrate 2 having the upper surface 21 that is the first surface and the lower surface 22 that is the second surface, which are in the front and back relationship with each other, with the first wiring pattern 28 being disposed on the upper surface 21 and the second wiring pattern 29 being disposed on the lower surface 22; the first electronic component 3 mounted on the upper surface 21 of the substrate 2; the second electronic component 4 mounted on the lower surface 22 of the substrate 2; and the mold portion that covers the second electronic component 4 without covering the first electronic component 3. The first electronic component 3 includes the first mounting terminal 39 disposed on the first relative surface 320 relative to the upper surface 21, and is bonded to the upper surface 21 via the conductive first bonding member B1 on the first relative surface 320, and the first mounting terminal 39 and the first wiring pattern 28 are electrically coupled to each other via the first bonding member B1. The second electronic component 4 includes the second mounting terminal 69, and is bonded to the lower surface 22 via the second bonding member B2 on the second relative surface 50 relative to the lower surface 22, and the second mounting terminal 69 and the second wiring pattern 29 are electrically coupled to each other via the bonding wire BW which is a conductive wire.

Accordingly, the problem described in the related art, that is, the problem that the mold material cannot be fully filled in the gap formed between the angular velocity sensors 3 x, 3 y, and 3 z and the substrate 2 due to the thickness of the first joining member B1, and a minute gap is formed in the portion does not occur. Therefore, even if the first bonding member B1 is melted by heat applied when the electronic device 1 is solder-mounted on the external substrate, unlike the related art, it is possible to effectively prevent wetting and spreading of the melted first bonding member B1 to an unintended portion, and it is possible to effectively prevent the occurrence of the electrical defects such as the short circuit, the disconnection, and the increase in the wiring resistance.

As described above, the first bonding member B1 is solder. Accordingly, mechanical coupling and electrical coupling between the angular velocity sensors 3 x, 3 y, and 3 z and the substrate 2 can be performed by the solder reflow. Therefore, the coupling can be easily and accurately performed. The first bonding member B1 is less deteriorated over time. Therefore, the manufacturing of the electronic device 1 is facilitated, and the reliability of the electronic device 1 is improved.

As described above, the angular velocity sensors 3 x, 3 y, and 3 z, which are the first electronic component 3, are packaged surface mount components. Accordingly, the angular velocity sensors 3 x, 3 y, and 3 z are excellent in the mechanical strength and easy to be mounted on the substrate 2. The second electronic component 4 includes the circuit element 6 electrically coupled to the angular velocity sensors 3 x, 3 y, and 3 z. Accordingly, the angular velocity sensors 3 x, 3 y, and 3 z and the circuit element 6 can be coupled in the electronic device 1, and the wiring for coupling the angular velocity sensors 3 x, 3 y, and 3 z and the circuit element 6 can be shortened. Therefore, noise is less likely to be added to the detection signals output from the angular velocity sensors 3 x, 3 y, and 3 z, and the angular velocity around each axis can be accurately detected.

As described above, the circuit element 6 is a bare chip. Accordingly, it is possible to reduce the size and the cost of the circuit element 6.

As described above, the angular velocity sensors 3 x, 3 y, and 3 z are physical quantity sensors each including the package 31 and the physical quantity detection element 34 accommodated in the package 31. The circuit element 6 includes the interface circuit 62 that communicates with the outside. Accordingly, the electronic device 1 can be mounted on various electronic components and has high convenience and demand.

As described above, the first electronic component 3, which is the physical quantity sensor, is the angular velocity sensors 3 x, 3 y, and 3 z. The second electronic component 4 includes the acceleration sensor 5 in addition to the circuit element 6. The acceleration sensor 5 is bonded to the lower surface 22. The circuit element 6 is bonded to the acceleration sensor 5. The circuit element 6 is electrically coupled to the angular velocity sensors 3 x, 3 y, and 3 z and the acceleration sensor 5 via the bonding wire BW. Accordingly, the electronic device 1 can be used as a composite sensor capable of independently detecting the angular velocity and the acceleration. Therefore, the electronic device 1 can be mounted on various electronic components and has high convenience and demand. Since the shape of the acceleration sensor 5 in the plan view is larger than the shape of the circuit element 6 in the plan view, the acceleration sensor 5 and the circuit element 6 can be disposed in a well-balanced manner by bonding the acceleration sensor 5 to the lower surface 22 and bonding the circuit element 6 to the acceleration sensor 5.

As described above, the electronic device 1 includes the plurality of leads 71 bonded to the substrate 2 and electrically coupled to the second wiring pattern 29. The coupling portion between the substrate 2 and the leads 71 is covered with the mold portion 9. Accordingly, it is possible to protect the coupling portion from moisture, dust, impact, and the like.

As described above, the electronic device 1 includes the cap 8 which includes the base portion 81 having the recess 811 that opens to the upper surface 21 side, and the flange portion 82 protruding from the end portion of the base portion 81 on the upper surface 21 side, which is disposed on the upper surface 21 so as to accommodate the first electronic component 3 in the recess 811, and in which the flange portion 82 is in contact with the upper surface 21. The flange portion 82 is bonded to the substrate 2 by the mold portion 9. Accordingly, the height of the electronic device 1 can be reduced. It is also possible to prevent contamination of the inside of the cap 8. Therefore, the electronic device 1 is small and has high reliability.

As described above, the substrate 2 is a ceramic substrate. Accordingly, the substrate 2 having high corrosion resistance is obtained. The substrate 2 having excellent mechanical strength is obtained. Therefore, the electronic device 1 having excellent long-term reliability is obtained.

Second Embodiment

FIG. 11 is a cross-sectional view showing an electronic device according to a second embodiment.

The present embodiment is the same as the first embodiment described above except that the arrangement of the acceleration sensor 5 and the circuit element 6 is different. In the following description, the present embodiment will be described with a focus on the difference from the above embodiment, and a description of similar matters will be omitted. In FIG. 11, the same reference numerals are given to configurations similar to those according to the above embodiment.

As shown in FIG. 11, in the electronic device 1 according to the present embodiment, the circuit element 6 is bonded to the lower surface 22 via the second bonding member B2 on the upper surface thereof, that is, a second relative surface 600 relative to the lower surface 22 of the substrate 2. The acceleration sensor 5 is bonded to the lower surface of the circuit element 6 via the third bonding member B3 on the upper surface thereof, that is, a third relative surface 500 relative to the lower surface of the circuit element 6. In the present embodiment, since a shape of the circuit element 6 in a plan view is larger than a shape of the acceleration sensor 5 in the plan view, the circuit element 6 is bonded to the substrate 2, and the acceleration sensor 5 is bonded to the circuit element 6. Accordingly, the acceleration sensor 5 and the circuit element 6 can be disposed on the substrate 2 in a well-balanced manner.

As described above, in the electronic device 1 according to the present embodiment, the first electronic component 3, which is a physical quantity sensor, is the angular velocity sensors 3 x, 3 y, and 3 z. The second electronic component 4 includes the acceleration sensor 5 in addition to the circuit element 6. The circuit element 6 is bonded to the lower surface 22. The acceleration sensor 5 is bonded to the circuit element 6. The circuit element 6 is electrically coupled to the angular velocity sensors 3 x, 3 y, and 3 z and the acceleration sensor 5 via the bonding wire BW. Accordingly, the electronic device 1 can be used as a composite sensor capable of independently detecting the angular velocity and the acceleration. Therefore, the electronic device 1 can be mounted on various electronic components and has high convenience and demand. Since the shape of the circuit element 6 in the plan view is larger than the shape of the acceleration sensor 5 in the plan view, the circuit element 6 and the acceleration sensor 5 can be disposed in the well-balanced manner by bonding the circuit element 6 to the lower surface 22 and bonding the acceleration sensor 5 to the circuit element 6.

Even with such a second embodiment, the same effects as those of the first embodiment can be exerted.

Third Embodiment

FIG. 12 is a cross-sectional view showing an electronic device according to a third embodiment.

The present embodiment is the same as the second embodiment described above except that the second electronic component 4 is electrically coupled to the second wiring pattern 29 via the second bonding member B2 instead of the bonding wire BW. In the following description, the present embodiment will be described with a focus on the difference from the above embodiments, and a description of similar matters will be omitted. In FIG. 12, the same reference numerals are given to configurations similar to those according to the above embodiments.

As shown in FIG. 12, in the circuit element 6 according to the present embodiment, a plurality of second mounting terminals 69 are disposed not only on the lower surface but also on the second relative surface 600 relative to the lower surface 22 of the substrate 2. The circuit element 6 is bonded to the lower surface 22 of the substrate 2 via the conductive second bonding member B2 on the second relative surface 600. The second mounting terminal 69 is electrically coupled to the second wiring pattern 29 via the second bonding member B2. The second bonding member B2 is various metal bumps such as gold bumps and silver bumps. Accordingly, it is possible to easily and accurately couple the circuit element 6 and the substrate 2.

The second bonding member B2 has a melting point higher than that of the solder as the first bonding member B1. More specifically, the second bonding member B2 has such a melting point that the second bonding member B2 is not melted by heat applied during a manufacturing step of the electronic device 1 or during solder reflow when the electronic device 1 is solder-mounted. The melting point of the second bonding member B2 is not particularly limited, and is preferably higher than the melting point of the solder as the first bonding member B1 by 50° C. or more, and more preferably by 100° C. or more. Accordingly, it is possible to effectively prevent melting of the second bonding member B2 at the time of the solder reflow.

By setting a melting point of the second bonding member B2 to be higher than a melting point of the solder which is the first bonding member B1, the following effects can be exerted. In the present embodiment, a gap G1 is formed between the circuit element 6 and the substrate 2 by a thickness of the second bonding member B2. Therefore, similarly to the related art, the gap G1 is not sufficiently filled with the mold material, and a minute gap may be generated in the portion. However, the second bonding member B2 does not melt even by solder reflow, and does not wet and spread in the minute gap. Therefore, it is possible to effectively prevent the occurrence of electrical defects such as a short circuit, a disconnection, and an increase in wiring resistance.

The electronic device 1 is described above. The electronic device 1 includes: the substrate 2 having the upper surface 21 that is the first surface and the lower surface 22 that is the second surface, which are in the front and back relationship with each other, with the first wiring pattern 28 being disposed on the upper surface 21 and the second wiring pattern 29 being disposed on the lower surface 22; the first electronic component 3 mounted on the upper surface 21 of the substrate 2; the second electronic component 4 mounted on the lower surface 22 of the substrate 2; and the mold portion 9 that covers the second electronic component 4 without covering the first electronic component 3. The first electronic component 3 includes the first mounting terminal 39 disposed on the first relative surface 320 relative to the upper surface 21, and is bonded to the upper surface 21 via the conductive first bonding member B1 on the first relative surface 320, and the first mounting terminal 39 and the first wiring pattern 28 are electrically coupled to each other via the first bonding member B1. The second electronic component 4 includes the second mounting terminal 69 disposed on the second relative surface 600 relative to the lower surface 22, and is bonded to the lower surface 22 on the second relative surface 600 via the conductive second bonding member B2 having the melting point higher than that of the first bonding member B1, and the second mounting terminal 69 and the second wiring pattern 29 are electrically coupled to each other via the second bonding member B2.

Accordingly, even if the mold material cannot be fully filled into the gap formed between the circuit element 6 and the substrate 2 due to the thickness of the second bonding member B2, and a minute gap is formed at the portion, it is possible to prevent the wetting and spreading of the second bonding member B2 in the minute gap. Therefore, it is possible to effectively prevent the occurrence of the electrical defects such as the short circuit, the disconnection, and the increase in the wiring resistance.

As described above, the second bonding member B2 is a metal bump. Accordingly, it is possible to easily and accurately couple the circuit element 6 and the substrate 2.

Even in such a third embodiment as described above, the same effects as in the above described first embodiment can be obtained.

As mentioned above, although the electronic device according to the present disclosure is described based on illustrated embodiments, the present disclosure is not limited thereto. A configuration of each part can be replaced with any configuration having a similar function. Further, any other constituents may be added to the present disclosure. The embodiments may be combined as appropriate. 

What is claimed is:
 1. An electronic device comprising: a substrate having a first surface and a second surface that are in a front and back relationship with each other, a first wiring pattern being disposed on the first surface, and a second wiring pattern being disposed on the second surface; a first electronic component mounted on the first surface of the substrate; a second electronic component mounted on the second surface of the substrate; and a mold portion that covers the second electronic component without covering the first electronic component, wherein the first electronic component includes a first mounting terminal disposed on a first relative surface relative to the first surface, and is bonded to the first surface on the first relative surface via a conductive first bonding member, and the first mounting terminal and the first wiring pattern are electrically coupled to each other via the first bonding member, and the second electronic component includes a second mounting terminal, and is bonded to the second surface via a second bonding member on a second relative surface relative to the second surface, and the second mounting terminal and the second wiring pattern are electrically coupled to each other via a conductive wire.
 2. An electronic device comprising: a substrate having a first surface and a second surface that are in a front and back relationship with each other, a first wiring pattern being disposed on the first surface, and a second wiring pattern being disposed on the second surface; a first electronic component mounted on the first surface of the substrate; a second electronic component mounted on the second surface of the substrate; and a mold portion that covers the second electronic component without covering the first electronic component, wherein the first electronic component includes a first mounting terminal disposed on a first relative surface relative to the first surface, and is bonded to the first surface on the first relative surface via a conductive first bonding member, and the first mounting terminal and the first wiring pattern are electrically coupled to each other via the first bonding member, and the second electronic component includes a second mounting terminal disposed on a second relative surface relative to the second surface, and is bonded to the second surface on the second relative surface via a conductive second bonding member having a melting point higher than that of the first bonding member, and the second mounting terminal and the second wiring pattern are electrically coupled to each other via the second bonding member.
 3. The electronic device according to claim 1, wherein the first bonding member is solder.
 4. The electronic device according to claim 2, wherein the second bonding member is a metal bump.
 5. The electronic device according to claim 1, wherein the first electronic component is a packaged surface mount component, and the second electronic component includes a circuit element electrically coupled to the surface mount component.
 6. The electronic device according to claim 5, wherein the circuit element is a bare chip.
 7. The electronic device according to claim 5, wherein the surface mount component is a physical quantity sensor including a package and a physical quantity detection element accommodated in the package, and the circuit element includes an interface circuit that communicates with the outside.
 8. The electronic device according to claim 7, wherein the physical quantity sensor is an angular velocity sensor, the second electronic component includes an acceleration sensor in addition to the circuit element, the acceleration sensor is bonded to the second surface, and the circuit element is bonded to the acceleration sensor, and the circuit element is electrically coupled to the angular velocity sensor and the acceleration sensor via the wire.
 9. The electronic device according to claim 7, wherein the physical quantity sensor is an angular velocity sensor, the second electronic component includes an acceleration sensor in addition to the circuit element, the circuit element is bonded to the second surface, and the acceleration sensor is bonded to the circuit element, and the circuit element is electrically coupled to the angular velocity sensor and the acceleration sensor via the wire.
 10. The electronic device according to claim 1, further comprising: a plurality of leads bonded to the substrate and electrically coupled to the second wiring pattern, wherein a coupling portion between the substrate and the leads is covered with the mold portion.
 11. The electronic device according to claim 1, further comprising: a cap that has a base portion having a recess that opens to a first surface side, and a flange portion protruding from an end portion of the base portion on the first surface side, that is disposed on the first surface so as to accommodate the first electronic component in the recess, and in which the flange portion is in contact with the first surface, wherein the flange portion is bonded to the substrate by the mold portion.
 12. The electronic device according to claim 1, wherein the substrate is a ceramic substrate. 